The present invention relates to an organopolysiloxane composition or, more particularly, to an organopolysiloxane composition crosslinkable into a gel-like form useful for protection of electronic components even at an extremely low temperature.
It is widely practiced in the electric and electronic industries to protect, in particular, various kinds of devices or components in electronic circuits such as power transistors, integrated circuits, capacitors and the like against mechanical damages and influences of heat and moisture from the ambience by potting or encapsulation with a gel-like material formed from a crosslinkable organopolysiloxane composition. A demand in recent years for such a crosslinkable organopolysiloxane composition is that the gel-like material formed therefrom has stable characteristics of protection for electronic components even at an extremely low temperature in order to meet the requirement in the space industry and other fields under rapid progress.
A means hitherto undertaken for improving the cold resistance of the organopolysiloxane composition is to introduce a substantial amount of phenyl groups into the molecular structure of the organopolysiloxane while a composition based on a high-phenyl organopolysiloxane has a problem of decreased excludability of bubbles contained in the liquid composition to cause a decrease in the workability therewith. Another means for the same purpose hitherto undertaken is to introduce trifunctional siloxane units CH.sub.3 SiO.sub.1.5 into the molecular structure of the organopolysiloxane. A problem in this way is the difficulty in controlling the viscosity of the organopolysiloxane so that good reproducibility can hardly be expected in the performance of the organopolysiloxane composition relative to the behavior of gelation and reliable cold resistance after crosslinking.